The logging recognition for the infill and the filling degree in karst cave

The large oil-gas oilfield, discovered in the Tarim Basin of Xinjiang, has more than 0.1 billion tons OOIP. Cave carbonate reservoir is one of very important reservoir types, the effectiveness of such reservoir depends on filling degree of cave, because of the reservoir’s horizontal distance can extend to a few meters or even dozens of meters, far exceeding the depth of the detection equipment, so it is still a technical puzzle to recognize effectively the infill and the filling degree in karst cave. The ancient caves’ logging response characteristic with different filling degree and filler in the conventional well logs, electric array acoustic imaging, array sonic image and cross-plot analysis to identify the character of the cave filling are analyzing in conjunction with identifier such as drilling, logging, well testing and seismic in the paper. It is concluded that the cave reservoirs can be divided into completely filled, half filled and unfilled types according to the analysis.